Does the 3 Gb Switch matter with 6 Gb of Ram

[aretap]

From my understanding in a 32-bit system with 4 Gb the OS dedicates 2 Gb to it and allows 2 Gb to go to other apps. The Revit 3 Gb switch allocates 3 Gb to the Revit app and only 1 Gb to the OS. However, in a 64-bit machine I can use LOTS more ram and thus am wondering if I have 6 Gb of ram installed will the OS then still dedicate 2 Gb to it and then leave me 4 Gb for other applications (thus actually giving more RAM to Revit or can Revit only use 3 Gb??). Or does it split it again making the ratio 3 Gb to 3 Gb inevitably still giving Revit 3 Gb the same as the switch. Or am I missing something. Just trying to figure out whether using the switch is helping or hurt and whether I would benefit from even more ram say like 8 Gb.

[sandovala]

We have a a 64 bit machine in the office with 8 gigs of ram, Autodesk informed me that Revit is a 32 bit program, meaning that the maximum amount of ram that I can take advantage of is 2GB, even with the 3GB switch on our 32 bit computers, running a a big file, we noticed crashes once Revit went past that 2GB threshold. What it does help is with the more ram on a 64 bit machine you can run more apps and run another session of Revit increasing your productivity. But trying to run a singular session you won't get any real benefit of the added ram. Hope this helps

[twiceroadsfool]

Im not so sure that is accurate. While i cannot add to the conversation of a 64 bit system and adding more memory, running the 3GB switch has certainly enabled us to work on larger files with less incidents.

In one specific case, AutoDesk Tech support told us this was the solution for a persistant "crash during STC" issue we were having, and enabling the 3GB switch has allowed Revit to use more Virutal Memory without getting terminated by Windows.

Without enabling it, some of our workstations that have less memory will simply Fatal Error or terminate Revit during a Save to Central...

[gordie_v]

It is my understanding that the 3GB switch has nothing to do with RAM
Windows XP can handle a max of 4GB RAM
and 2GB Virtual memory

with the switch enabled it increases the virtual Memory to 3GB
but has no impact on physical Ram

then with a 64 bit Windows I don't see a need for the switch because you can now go beyond the 4GB RAM

I could be wrong but this is my understanding of it.

[sandovala]

Don't get me wrong it has added a great deal of stability, all our machines are running on the 3GB switch, And the stability on working on large projects has greatly increased because of the switch, but from what they have told me(Autodesk), Revit will see the more ram, but it is limited because it's a 32 bit program, the added RAM adds stability to your system, but from a performance standpoint 2 is the physical memory limit when running one session of Revit, your VM will eclipse that threshold, but the moment the physical RAM hits 2, you will error out.

[aretap]

So do i turn it on or not??? Key question is it going to hurt my performance by using it

[sandovala]

It's not going to hurt your performance, it's really not necessary on 64 bit machines, definitely something to do on 32 bit machines.

[Wes Macaulay]

So do i turn it on or not??? Key question is it going to hurt my performance by using itIf you're not on Windows 64-bit then you're wasting your money. And if you're on 64-bit Windows you do not need the switch.

[patricks]

My dual dual-core Xeon machine with 4GB RAM shows XP's paging file size set to 4092 MB already, so would the 3GB switch even apply to me?

[iru69]

From my understanding in a 32-bit system with 4 Gb the OS dedicates 2 Gb to it and allows 2 Gb to go to other apps. The Revit 3 Gb switch allocates 3 Gb to the Revit app and only 1 Gb to the OS. However, in a 64-bit machine I can use LOTS more ram and thus am wondering if I have 6 Gb of ram installed will the OS then still dedicate 2 Gb to it and then leave me 4 Gb for other applications (thus actually giving more RAM to Revit or can Revit only use 3 Gb??). Or does it split it again making the ratio 3 Gb to 3 Gb inevitably still giving Revit 3 Gb the same as the switch. Or am I missing something. Just trying to figure out whether using the switch is helping or hurt and whether I would benefit from even more ram say like 8 Gb.
You're correct that the /3GB switch allows for an application to take advantage of an additional 1 GB of virtual address space beyond the 2 GB standard on 32-bit Windows. The application has to be enabled as "Large Address Aware" (by the application developer) to take advantage of it. Based on other threads which have indicated that Autodesk support has informed them to enable the /3GB switch, it appears that Revit has been enabled with such support. Having more than 4 GB of RAM on 32-bit Windows is pointless.

You would not use a /3GB switch with 64-bit Windows. I've read that 64-bit Windows will allow an application that has been made "Large Address Aware" to use up to 4 GB of address space. It's still limited to 4 GB because Revit is still a 32-bit application.


It is my understanding that the 3GB switch has nothing to do with RAM
Windows XP can handle a max of 4GB RAM
and 2GB Virtual memory

with the switch enabled it increases the virtual Memory to 3GB
but has no impact on physical Ram

then with a 64 bit Windows I don't see a need for the switch because you can now go beyond the 4GB RAM

I could be wrong but this is my understanding of it.
I think you're kind of right and kind of wrong, and you might be a bit confused at the same time (and I’m not an expert either, so keep that in mind)...

Virtual address space is the amount of memory addresses, physical or not, that can be addressed by the OS and applications. This is also referred to as virtual memory. All regular applications use virtual address space. The hardware will translate the addresses to physical RAM.

If you run out of physical RAM, the OS will transparently (except for that noticeable slowdown in performance) swap applications and data out of the physical RAM into a page (swap) file (also often referred to as virtual memory, though I like the term virtual RAM better).

The 4 GB can be divided between physical RAM and virtual RAM (page/swap files).

It would be really nice if someone could pull some strings and get all the facts directly from the Factory and make it a sticky in the Hardware forum - there's so much confusion and misinformation on this topic.

[bob.parker]

Revit will only use 1.5Gb of ram no matter what you through at it. The only benifit you'll get by adding more ram, up to 3Gb and using the 3Gb switch, is that extra 1Gb of ram, which will be allocated for the system, which will leave 1.5Gb of ram for Revit and an extra 512Mb of ram for other applications you might have running. If Windows isn't using all of the 1Gb allocated with the 3Gb switch then it will allow you to use it for programs.

x64 will allow you 32Gb of ram per proccessor, but again Revit, for now, is a single core 1.5Gb application.

Spend the money on a 512 video card.

[twiceroadsfool]

Revit will only use 1.5Gb of ram no matter what you through at it. The only benifit you'll get by adding more ram, up to 3Gb and using the 3Gb switch, is that extra 1Gb of ram, which will be allocated for the system, which will leave 1.5Gb of ram for Revit and an extra 512Mb of ram for other applications you might have running. If Windows isn't using all of the 1Gb allocated with the 3Gb switch then it will allow you to use it for programs.

x64 will allow you 32Gb of ram per proccessor, but again Revit, for now, is a single core 1.5Gb application.

Spend the money on a 512 video card.

Im not sure where your getting this information from, but i can definetely show a screen shot tomorrow mornign of Revit using much more than 1.5GB of memory. I can get you a screen shot of the Physical memory over 2GB, and the Virtual over 1.5, if youd like, lol...

[Wes Macaulay]

Revit will only use 1.5Gb of ram no matter what you through at it. The only benifit you'll get by adding more ram, up to 3Gb and using the 3Gb switch, is that extra 1Gb of ram, which will be allocated for the system, which will leave 1.5Gb of ram for Revit and an extra 512Mb of ram for other applications you might have running. If Windows isn't using all of the 1Gb allocated with the 3Gb switch then it will allow you to use it for programs.

x64 will allow you 32Gb of ram per proccessor, but again Revit, for now, is a single core 1.5Gb application.

Spend the money on a 512 video card.We've seen Revit use over 3Gb of RAM, particularly when executing a save to central on large projects. As noted in this thread, Revit is 32 bit so it cannot access any more RAM than that, and I don't know if it is limited to the "low range" of available RAM, or higher addresses.

One of the Revit developers has told us that Revit's video RAM requirements do not at this time exceed 32Mb. A 128 Mb RAM video card will thus more than suffice for Revit 2008; perhaps that will change in the future.

[iru69]

Revit will only use 1.5Gb of ram no matter what you through at it. The only benifit you'll get by adding more ram, up to 3Gb and using the 3Gb switch, is that extra 1Gb of ram, which will be allocated for the system, which will leave 1.5Gb of ram for Revit and an extra 512Mb of ram for other applications you might have running. If Windows isn't using all of the 1Gb allocated with the 3Gb switch then it will allow you to use it for programs.

x64 will allow you 32Gb of ram per proccessor, but again Revit, for now, is a single core 1.5Gb application.

Spend the money on a 512 video card.
Top to bottom, none of this is true or makes sense.

[david.metcalf]

Come on I am getting ticked off. : ) lets get some solid information from a source that is involved in the interlacing of the software and hardware enviroment.

[BomberAIA]

Has anyone used the 3 gig switch with bootcamp?

[BMcCallum]

What about using the /3GB switch with Parallels?

I rarely use BootCamp any more, Parallels has plenty of power.

Anybody? Phil?

[bowlingbrad]

I just sent a SR begging autodesk to give us the real deal. Not that we all haven't tested this to death, but, I want something from the horses mouth.

[sandovala]

I just sent a SR begging autodesk to give us the real deal. Not that we all haven't tested this to death, but, I want something from the horses mouth.


Thanks

I agree, can't wait to see what the factory has to really say so we can get the facts straight

[bowlingbrad]

Here is what I got back from Autodesk Support:


Thank you for contacting Autodesk Support. Here is the recommended resolution to your Support Request:

We have two documents which discuss Revit’s use of memory. They are Technical Solutions TS1060354 (http://usa.autodesk.com/getdoc/id=TS1060354) and TS1060353 (http://usa.autodesk.com/getdoc/id=TS1060353).

For the video memory, I asked Development for information on this and they told me Revit uses up to 128 MB of RAM.

The first doc describes maximizing page file size. The second talks about the 3GB switch. The third is self-explanitory.

HTH

[iru69]

Here is what I got back from Autodesk Support...
Thanks Brad. Actually, I think those have been posted somewhere around here before.